#define _CRT_SECURE_NO_WARNINGS 1


#include <stdio.h>
int fun(int n)
{
	if (n == 1 || n == 2)
		return 1;
	else
		return fun(n - 1) + fun(n - 2);
}
int main() {
	int n = 0;
	scanf("%d", &n);
	printf("%d", fun(n));
	return 0;
}